Tool steel. I bought a piece of drill rod from mcmaster-carr. It was cheap @$5 IIRC. You might be able to get away with something like 8620, but for the price of the drill rod I wasn't going to fool around with anything else. I know I've still got some leftover, if I can find it, I'll send you a piece.

Thank you very much 7.62 x 39 for the offer of the drill rod. I checked in the "scrap" bin in my little shop and found a piece from a previous project. Now I need to find the time to get to it!

Myself I've only had the 2 Mini 30's throughout the years, but I noticed they both would fling the cases far far away too. Must be the 30's were over gassed too, or at least that's my assumption. Anyone else run into that ?

The lighter barreled early mini 14 barrels (.560" dia barrel) take the .295" long bushing. I usually go for .186" dia for a bit tighter fit on both the mini 14 and 30's. You can also add .001-002" on length for a tighter fit, I would not recommend more than that, or to be undersized from factory size bushings in O.D. and length.
the Mini 30 (.625" barrel OD) will take the .264" length bushing, again you can add 1-2 thousandths to .265"-.0266" but I would not recommend more than that.

Are you sure you have the right length bushings in the correct rifles?
a mini 30 generally works best with a .050-.060" gas hole in the bushing and gives 8'-12' ejection distance.
A .040" bushing will give about 8-10' ejection distance in the mini 14. (I prefer a .042-045" on the older mini 14's) I have made several hundred bushings for minis and that is about what seems to work.
A too short bushing (.264") would explain the long ejection distance in the 14, with gas leaking around the bushing length, and a too long .040" (too small from my experience for a 30) would explain the short ejection distance in the 30. Placed side by side you can see the difference in length with the eye and compare next to the factory ones if you do not have a micrometer or caliper on hand. The factory mini 30 will be shorter and have @ a .100" gas hole in it. I would double check to make sure if you have any doubt, too long a bushing in the 30 is not a good thing for the gas block. Eventually it will peen over from the heat and pressure and make it a dickens to get out of the gas block.

5'-8' is on the edge of marginal for ejection distance in my opinion on any mini except for a bench rifle. I usually go for 8' minimum and 12'-15' max for a reliable bench/field mini. You will find that different brands of ammo or hand-loads will have different ejection distances relating to the powder loadings in the same mini with the same size gas bushing. Wolf 223 will not have the power or ejection distance of NATO 5.56 ammo. NATO ammo may function just fine at 6' ejection distance, Wolf may not and short stroke. Different capacity magazines will affect performance also, a 5 round mag may function fine, a 20 round mag may short stroke occasionally due to the increased spring pressure on a full 20-30 round mag. It will put more upward pressure on the bolt riding over the ammo in the magazine and require more energy for the bolt to cycle and strip a round off than a 5 round magazine with less spring pressure. Cold temperature may come into play also, as the powder doesn't burn as fast at really cold temps = less gas power to cycle. Dirt and crud can impact cycling and slow the action also. While the mini's can be over-gassed to the point they negatively effect performance they can benefit from reducing gas bushing hole size and the gas pressure, but be aware that under-gassing can affect reliability. Over-gassed mini? I worked on a 1/7 twist mini 14 that threw brass 60' (20 yards) a .043" bushing tamed it to 12'-15' and kept it every bit as reliable and absolutely made the action smoother cycling and less violent and also made the mini easier to keep on target. A reduced size bushing in a mini 30 (.060") makes the mini 30 feel more like a mini 14 with no loss of reliability. When you get the gas controlled just right on a ranch style mini you see the ejection angle change to 1-2 o'clock instead of 3-4 o'clock, then it's tuned in and they run nice and smooth. Also when you get the gas under control you get the added benefit of taking the ding out of the brass on ejection.